1. Field of the Invention
This invention generally relates to an angular velocity sensor, and more particularly, to an angular velocity sensor that employs a piezoelectric vibrator.
2. Description of the Related Art
An angular velocity sensor detects the angular velocity when an object is rotating. Angular velocity sensors are in use for avoiding blurring of images due to hand movement in taking a picture, position detection systems such as car navigation systems, and attitude control systems for automobiles and robots. Any inclination of a detection axis against a detection reference plane causes a detection error or an improper detection of another axis. In the above-mentioned case, an accurate angular velocity cannot be detected. Therefore, a control system equipped with the angular velocity sensor will suffer from various problems caused resulting from angular errors in detection. For example, with respect to a car navigation system, the angular velocity sensor is generally housed in the dashboard of a car. In the case where the control system equipped with the angular velocity sensor is installed in the dashboard, if the detection axis is parallel to the ground surface that is the reference plane, the angular velocity can be detected accurately.
The dashboards of a number of cars, however, are not parallel to the ground surface. In the case where the control system is installed in an inclined dashboard, the detection axis of the angular velocity sensor is also inclined, the detection error of the angular velocity becomes greater, and similarly, the improper detection of another axis occurs more often. FIGS. 1A and 1B show the above-mentioned case. The horizontal axis in FIG. 1A denotes the angle of sensor inclination (°), and the vertical axis in FIG. 1A denotes the detection error of angular velocity (%). The horizontal axis in FIG. 1B denotes the angle of sensor inclination (°), and the vertical axis in FIG. 1B denotes the improper detection of another axis (%). In addition, it is necessary to newly install a tilting table in a dashboard or attach the tilting table to the sensor, if the detection axis of the sensor needs to be parallel to the ground surface. As a result, a larger space is required.